1. Field of the Invention
The present invention relates to a wireless communicating method, a wireless communicating system, a communicating station, and a controlling station suitable for wirelessly transmitting chronologically continuous data streams (such as digital audio data and digital video data) and asynchronous data (such as commands) for example between digital audio units or between digital video units.
2. Description of the Related Art
Audio units and video units have been digitized as with for example CD (Compact Disc) players, MD (Mini Disc) recorders/players, digital VCRs, digital cameras, and DVD (Digital Versatile Disc) players. As personal computers have become common, systems that connect such digital audio units or digital video units to personal computers have been proposed. As an interface that accomplishes a system that connects such digital audio units or such digital video units to a personal computer, IEEE (Institute of Electronics Engineers) 1394 is becoming attractive.
The IEEE 1394 interface supports both an isochronous transmission mode and an asynchronous transmission mode. The isochronous transmission mode is suitable for transmitting chronologically continuous data streams such as video data and audio data at high speed. The asynchronous transmission mode is suitable for transmitting various commands and files. Since the IEEE 1394 interface supports both the isochronous transmission mode and the asynchronous transmission mode, when the IEEE 1394 interface is used, video data and audio data can be transmitted between digital audio units and between digital video units, respectively. With a personal computer connected to such digital units through the IEEE 1394 interface, the user can easily control and edit video data and audio data.
The IEEE 1394 interface is a wired interface. To structure such a system with a wired interface, cable connections are required. In addition, such cable connections tend to become complicated. Moreover, with a wired interface, it is difficult to connect units that are disposed in different rooms.
Thus, a digital audio unit or a digital video unit and a personal computer are connected with a wireless LAN (Local Area Network) so as to wirelessly communicate therebetween. As examples of the wireless LAN, CSMA (Carrier Sense Multiple Access) method and polling method are known.
However, in the conventional CSMA method and polling method, data streams such as video data and audio data cannot be transmitted at high speed. To solve such a problem, as with IEEE 1394, a wireless LAN that supports both an isochronous transmission mode that allows data streams such as video data and audio data to be transmitted at high speed and an asynchronous transmission mode that allows asynchronous data such as commands and files to be transmitted has been developed.
When each unit wirelessly communicates data with another unit through a wireless LAN, only a unit that communicates with another unit is set to an operation state. The other units that do not communicate are set to a sleep state.
In other words, when one unit wirelessly communicates data with another unit through a wireless LAN, if the wireless node of each unit is in the operation state, the unit consumes power. In contrast, wireless nodes that do not communicate are set to the sleep state. In other words, power supply to unnecessary circuit portions may be stopped. Alternatively, the operation clock frequency may be lowered.
As described above, conventional wireless LANs use the CSMA method or polling method. However, in the CSMA method or polling method, there is no way to determine whether or not a communicating party is in the sleep state. Thus, since wireless nodes that communicate with other wireless nodes cannot be set to the sleep state, the power consumption cannot be easily reduced.
Therefore, an object of the present invention is to a wireless communicating method, a wireless communicating system, a communicating station, and a controlling station that cause a non-communicating wireless node that is connected to a wireless LAN to enter into a sleep state so as to reduce power consumption.
A first aspect of the present invention is a wireless communicating method for a system having a plurality of communicating stations and a controlling station for controlling an accessing operation of the communicating stations, the controlling station being disposed between the communicating stations, a communication signal being transmitted and received between each of the communicating stations and the controlling station, the communication signal having a control area and a data area structured as a frame on time division basis, the method comprising the steps of causing a communicating station to transmit a communicating station state change request signal to the control station, causing the control station to transmit a communicating station state signal to the communicating station so as to enter the relevant communicating station into a sleep state, and causing a communicating station in the sleep state to receive a start command signal that causes the relevant communicating station to cancel the sleep state.
A second aspect of the present invention is a wireless communicating system having a plurality of communicating stations and a controlling station for controlling an accessing operation of the communicating stations, a communication signal being transmitted and received between each of the communicating stations and the controlling station, the communication signal having a control area and a data area structured as a frame on a time division basis, wherein a communicating station transmits a communicating station state change request signal to the controlling station, wherein the controlling station transmits a communicating station state signal to the communicating station so as to cause the communicating station to enter into a sleep state, and wherein a communicating station in the sleep state receives a start command signal so as to cause the communicating station to cancel the sleep state.
A third aspect of the present invention is a communicating station of a wireless communicating system having a plurality of communicating stations and a controlling station for controlling an accessing operation of the communicating stations, a communication signal being transmitted and received between each of the communicating stations and the controlling station, the communication signal having a control area and a data area structured as a frame on a time division basis, the communicating station comprising a communicating station state change request signal transmitting means for transmitting a communicating station state change request signal with which a communicating station requests the controlling station to set the communicating station to the sleep state, a communicating station state signal receiving means for receiving a communicating station state signal that represents whether or not a communicating station is in the sleep state, a start command signal receiving means for receiving a start command signal that causes the communicating station to cancel the sleep state, and a controlling means for transmitting the communicating station state change request signal that requests the controlling station to set the communicating station to the sleep state, receiving the communicating station state signal that causes the relevant communicating station to enter the sleep state, and receiving the start command signal that causes the communicating station to cancel the sleep state.
A fourth aspect of the present invention is a controlling station of a wireless communicating system having a plurality of communicating stations and a controlling station for controlling an accessing operation of the communicating stations, a communication signal being transmitted and received between the communicating stations and the controlling station, the communication signal having a control area and a data area structured as a frame on a time division basis, the controlling station comprising a communicating station state signal transmitting means for transmitting a communicating station state signal that represents whether or not a communicating station is in a sleep state, a start command signal transmitting means for transmitting a start command signal that causes the relevant communicating station to cancel the sleep state, a communicating station state change request signal receiving means for receiving a communication state change request signal with which a communicating station requests the controlling station to set it to the sleep state, and a controlling means for causing a communicating station to transmit the communicating station state signal so as to cause the communicating station to enter into the sleep state, the controlling station to transmit the communicating station state signal corresponding to the communicating station state change request signal, and the controlling station to transmit the start command signal to the communicating station so as to cause it to cancel the sleep state.
A communicating station transmits a communicating station state change request signal to a controlling station. The controlling station transmits a communicating station state signal to the communicating station so as to enter the communicating station into a sleep state. Thus, the local station can enter into the sleep state by itself. In addition, the local station can be entered into the sleep state corresponding a command received from the controlling station. A communicating station in the sleep state always receives at least a start command signal. Thus, the communicating station in the sleep state can cancel the sleep state by itself. In addition, the sleep state of the communicating station can be canceled corresponding to a command received from the controlling station.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.